The present invention generally relates to tools used for analysis during exploration drilling, and more specifically it relates to analysis tools that attach to drill stems for using during the process of drilling.
In drilling for minerals, hole diameters typically range from 3″ to 7″ and drill depths to a few hundreds of feet. The long steel drill stem transmits torque and downward force on the bit. The hammer is operated by compressed air supplied by the engine. Drilling involves the use of a hardened steel bit to penetrate a rock mass in order to extract samples for determining subsurface rock properties or to place explosives for breaking out rock mass.
A. Exploration Drilling
A property that is suspected to have economic deposit of useful minerals based on its geological setting determined by field work will have to be drilled to confirm those suspicion. Trenches may be dug to the investigate the subsurface, but the depth of trenches goes to about 30 feet, whereas the typical depth needed to traverse rich zones of valuable rock are a few hundred feet.
As the drill bit penetrates the rock, it cuts out cylinders of rock which are retrieved in the core barrel and stored by depth sequence in boxes. The boxes are logged by a geologist and transported to labs where the cores are prepared for analysis. The quality of the mineral deposit and an estimation of the amount of mineable mineral is determined from the exploration holes.
Due to the high cost of coring, exploration holes are spaced thousands of feet apart requiring extrapolation of data between the holes. Another problem is that core recovery may be low due to soft or broken rock in sections which leads to gaps in the data.
B. Mine Planning
When an area is being mined, it is necessary to know with confidence the quality of the minerals scheduled to be mined in the short term. The pertinent information for the land between exploration holes is uncertain since the holes are far apart. More holes are drilled with production drills rather than coring. Holes are drilled and the cuttings from the holes are collected in bags and labeled by depth intervals or by lithology predicted from the exploration holes. The bags are transported to labs for analysis. Since the rock samples are pulverized before they are brought up the borehole and collected, contamination may be an issue. Also, tests for physical rock properties from these samples can be challenging.
C. Rock Blasting
In many mining operations, the rock mass is too hard for direct mucking with a mechanical shovel or ripping up with a dozer. In such cases, blasting using explosives is done. Holes are drilled in a predetermined pattern near the rock face. Hole depth ranges from 10 feet to 100 feet with diameter ranging from 3 inches to 8 inches. The holes are loaded by a bulk truck with explosives according to the blast design and detonated. The rock falls to the floor in a muck pile which is then loaded to transport units for mineral processing.
Loading adjustments are made for the profile of the rock face to reduce fly rock and for effective breaking. In a layered rock face with varying rock properties, the explosive selection along the hole column may not be optimized leading to higher explosive ratios used to break the rock face. No automated loading exists based on rock properties or geology contact.
A method and apparatus for analyzing the subsurface conditions more accurately, quicker and less expensively is desirable.